JPS6042233B2 - Method for producing para-nitrosodiphenylamine hydrochloride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved process for preparing para-nitrosodiphenylamine (pNDPA) from diphenylamine (DPA) and alkyl nitrite in the presence of excess hydrogen chloride.

Alkyl nitrites are derived from substantially water-immiscible primary aliphatic alcohols, which also serve as reaction solvents. The resulting pNDPA of this method
The hydrochloride salt is extremely stable. After neutralization, pNDPA is recovered by crystallization. If desired, pNDPA can be hydrolyzed without isolation from the solvent to p-aminodiphenylamine, a known precursor to antioxidants and antiozonants, or reductively alkylated with a suitable ketone. Apply antiozonant directly
can be done.

It is well known that pNDPA hydrochloride slurries are unstable.

The instability of pNDPA hydrochloride reaction slurries in processes using alcohol and aromatic solvent systems is well known to those skilled in the art and is sometimes referred to as gelation. Occasionally, rapid decomposition was observed during the preparation of pNDPA hydrochloride in such two-solvent systems due to local overheating and possibly other causes. pNDPA hydrochloride slurry decomposes even at room temperature. If kept for more than a certain time, one notices that the red-brown mixture gradually darkens, and the viscosity of the reaction mass increases to such an extent that recovery of undecomposed products is no longer practical. For this reason, the reaction mass is neutralized as soon as possible once the reaction is complete.
The state of the prior art was summarized in US Pat. No. 4,034,042.

The shortcomings of previously disclosed methods related to the instability of the PNDPA hydrochloride reaction mass were discussed therein in some detail. US Patent No. 403404? The improvement claimed therein is to substantially increase the ratio of alcohol, usually methanol, to aromatic hydrocarbon solvent to keep the PNDPA hydrochloride in solution. However, this solvent system does not stabilize PNDPA hydrochloride and only moderates its degradation, thereby minimizing the possibility of uncontrolled gelation. After all, the reaction solution must be neutralized as soon as possible to prevent serious yield losses. US Patent No. 4034
PNDP in solution as disclosed in Figure 1 of No. 042
Hydrochloride A decomposes about 50% in about 4 hours at 40°C. It has been discovered that the PNDPA hydrochloride slurry made in accordance with the present invention is extremely stable when substantially water-immiscible higher saturated aliphatic alcohols are used as the solvent of the process.

For example, PNDPA hydrochloride was prepared at temperatures as high as 50'C without appreciable loss in yield. When using the solvents of this process, no type of rapid decomposition leading to gelation occurs. The production of alkyl nitrites from alcohols is a process known to those skilled in the art.

For example, the production of n-butanol nitrite from n-butanol requires 0 rg. synthesis, c01. V01.
2, 1943, 108. The alkyl nitrite of the present invention is usually in alcohol. 50% to 90%
(by weight) as a solution.

Usually solutions of about 60% to 70% by weight are used.
Although it is convenient as a practical idea to make the alkyl nitrite from the same alcohol that should be used as the solvent in the process, it is essential! It's not something. This practice greatly simplifies separation and recycling of process solvents. In this method, a solution of alkyl nitrite and DP
Combine with solution A.

It is convenient, but not essential, to use the same alcohol as solvent for the two reactants.

To this stirring mixture, subsurface, excess hydrogen chloride is added to form the PNDPA hydrochloride slurry of the present invention. Conversely, D in alcohol containing an appropriate excess amount of hydrogen chloride
The PNDPA hydrochloride of the present invention can also be produced by incremental addition of alkyl nitrite to a suspension of PA hydrochloride.

Either method produces high yields of PNDPA hydrochloride. When making the DPA solution, the amount of alcohol is adapted depending on the concentration of the nitrite solution used to provide a PNDPA hydrochloride slurry with the desired physical properties.

The concentration of PNDPA hydrochloride obtained at the end of the reaction can vary from about 1% to about 4% by volume of alcoholic solvent. However, concentrations of 20% to 25% are preferred. At this concentration, the reaction mass has good mixing and heat transfer properties. Moreover, the resulting slurry is easy to handle in subsequent finishing operations. Hydrogen chloride and/or
Alternatively, it is advantageous, although not essential, to add the alkyl nitrite at a fast rate commensurate with the removal of heat and then drive the reaction to completion.

The addition time can vary from about 1 hour to about 5 hours, but is preferably from 2 to 3 hours. The reaction mass is then stirred for 1 to 5 hours, or longer if necessary, depending on the rate of addition, excess hydrogen chloride used, and temperature. The presence of hydrogen chloride in excess of DPA is necessary to drive the reaction to completion. The intended molar ratio of hydrogen chloride to DPA for this process is approximately 1.5.
:1 to about 2.5:1. The preferred ratio is from 1.8:1 to 2.1:1. D.P.A.
It is also advantageous to use a molar excess of alkyl nitrite. The excess of alkyl nitrite that can be used is from about 0.1 to 20 mole percent over DPA. The preferred molar excess amount is about 8 to 10 mole percent. The nitration of DPA to give PNDPA hydrochloride is an exothermic process, so some cooling is required, especially during the first stage.

Nitration can be carried out at temperatures ranging from about 20°C to about 50°C. A preferred range is about 30°C to 35°C. Saturated aliphatic alcohols useful as solvents for this invention can be primary or secondary with hydrocarbon chains from C5 to ClO, which may be straight or branched, and from about 130°C to 200°C. It has a boiling point in the range of .

Primary alcohols are preferred as solvents in this process over secondary alcohols because they are less likely to participate in side reactions with hydrogen chloride to form water and alkyl chlorides. The increase in alkyl chloride byproducts in the recycled solvent necessitates removal of the byproducts from the alcohol. Moreover, even small losses of alcohol in this side reaction will adversely affect economics in commercial trials. Preferred alcohols of the invention are substantially immiscible with water.

Low losses of alcohol to the aqueous phase are also economically unacceptable on a commercial scale and generally require elaborate separation procedures for solvent recovery. Preferred alcohols for this process are primary saturated aliphatic alcohols having from C6 to C8 carbon atoms, which can be linear or branched.

Examples of such alcohols are n-hexanol, n-octanol, and 2-ethylhexanol. The most preferred alcohol is hexanol. When the reaction is complete, the PNDPA slurry is reduced to a pH of about 7 to about 14 by an inorganic base, usually sodium hydroxide.
to be processed.

It is usually desirable to stop adding base when the pH of the mixture reaches a pH of about 8 to about 9. Heat the mixture to 700-80°C at which point essentially all the PND
PA goes into solution in alcohol. If necessary, add more base to adjust the pH of the mixture again to a value of 8 to 9. The aqueous phase is discarded, the alcoholic phase is cooled and the PNDPA is recovered by crystallization. Preparation of p-nitrosodiphenylamine hydrochloride Example 1 A 1-stand, 4-unit container equipped with a thermometer, a stirrer, an air cooler and a gas inlet pipe.
D in hexanol (199q) in a round-bottomed flask.
A solution of PA (84.5q11.5 mol) was charged.

Alkyl nitrite (68y10.52 mol) was then added as a 68% solution in hexanol. Addition of hexyl nitrite causes a hidden exotherm, so a water bath is required to keep the temperature below 40°C. Then hydrogen chloride (38.
11.05 mol of 3f) was introduced under the water surface over a period of 2 hours, during which time the reaction mass was stirred and 30-
Maintain at 35°C, almost 37°C. The resulting red-brown slurry is stirred for an additional 4 hours while the temperature is maintained near 37C. PNDPA hydrochloride was filtered and diluted with hexane (20
0 mL) and air-dried at 60°C. 11 recovered
0.8f of PNDPA hydrochloride has a melting point of 150°C, decomposition, and D
The yield is 94.5% based on PA. Example 2 Example 1 was repeated except that the hexyl nitrite solution was added over 2 hours to the mixture of DPA hydrochloride and hydrogen chloride in hexanol at 30-35°C.

The resulting red-brown slurry was stirred for 4 hours at about 32°C. The yield of PNDPA was essentially the same as in Example 11. Preparation of p-Nitrosodiphenylamine Example 3 PNDPA hydrochloride was prepared according to the procedure of Example 1, but the salt was not isolated.

Instead, add 1 14% solution of sodium hydroxide to the slurry.
Add drops and process. The exotherm of neutralization was controlled by an ice-water bath to prevent the temperature of the reaction mass from rising above 50°C. The addition of sodium hydroxide was stopped when the PH of the reaction mass reached a value between 8 and 9. Stir at 40-50°C for 30
for a longer time, then heat the mixture to 70-80'C,
During that time, the pH dropped to below 7. The pH was adjusted to approximately 8.5 by addition of sodium hydroxide solution.

The aqueous phase was separated and discarded while the temperature was kept at 70-80°C. The hexanol phase was kept at approximately 5 °C overnight and the PND
The blue-black crystals of PA were filtered off, washed with hexane and air-dried at 60° C. overnight. Melting point 143-145°C0)P
86.4 g of NDPA was recovered. The mother liquor was concentrated to about 70 da by distillation under vacuum and the solution was kept at 5°C overnight. 9.1 g of PNDPA with a melting point of 139-143°C was recovered. The combined yield is 96.5% based on DPA. Example 4 The procedure of Example 3 was essentially followed using the following ingredients: 7 diphenylamine 84.5 g (0.5 mole) 2-
455 y of ethylhexanol, 827 y of 2-ethylhexyl nitrite (0.52 mol), 38.3 y of HCl gas as a 68% solution in 2-ethylhexanol (1
．． After neutralization, the blue-black crystals of n-nitrosodiphenylamine were isolated by filtration, washed with hexane and dried.

A product of 87y was obtained (yield 87.9%, melting point 142-
After separating the alcoholic phase of the mother liquor from the aqueous phase and keeping it at room temperature for a period of time, the blue-black crystals were filtered off, washed with hexane and dried.

An additional 6.0 Da of product was thus obtained (melting point 14
2-145°C). Overall Yield: 94.0% Example 5 The general procedure of Example 3 was again adopted using the following components: diphenylamine di-84.5y (0.5 mol) n-
Pentanol ni 207y Nitrite n-pentyl ni 60.8
y (0.5 mol) in HCl gas as a 67% solution in pentanol (1.05 mol). In this case, the neutralized p-nitrosodiphenylamine slurry was prepared at 5 °C.
It was kept for about ■ hours.

The resulting crystals were filtered off, washed with hexane and dried.
It gave 8.6q (89.5% yield) of product. The mother liquor was treated as described above but no addition product was obtained. Reference Example Preparation of p-aminodiphenylamine PNDPA was made according to the procedure of Example 3, but the product was not isolated; instead, a hexanol slurry was charged to a single autoclave and a 5% Pd/C catalyst (
2.5f) at 60-65° C. at hydrogen pressures from 500 to 800 pSi.

Claims (1)

Claims: 1. Para-nitrosodiphenylamine hydrochloride comprising reacting diphenylamine, a C_5-C_1_0 alkyl nitrite and anhydrous HCl in the presence of a C_5-C_1_0 aliphatic alcohol, essentially in the absence of an aromatic solvent. Method of manufacturing salt. 2. The method of claim 1 further comprising converting para-nitrosodiphenylamine hydrochloride to para-nitrosodiphenylamine by addition of a base. 3. The method of claim 1, wherein the aliphatic alcohol is pentanol, hexanol or 2-ethylhexanol. 4. The method according to claim 3, wherein the alkyl nitrite is pentyl nitrite, hexyl nitrite or 2-ethylhexyl nitrite. 5. The method of claim 1, wherein the molar ratio of HCl to diphenylamine is from 1.5/1 to 2.5/1.